As a recording media of high speed, sufficient capacity, strong reliability and low cost, disk drives are widely used for digital information recording. With the development of technology for several years, recording density of a disk drive has been developed to exceed over 100 GB per square inch. A plurality of head arm assemblies each of which is comprised of a drive arm and a head gimbal assembly (HGA) disposed on distal end of the drive arm are provided in a disk drive, corresponding to number of disks which function as recording medium. The HGA includes a slider. The slider has a read/write portion incorporating at least one of write element for writing information to the recording medium and read element for reading information from the recording medium. The read/write portion is disposed at one end of the slider. A surface of the slider opposing the recording medium is referred as an air bearing surface (ABS).
When slider performs information recording/reproducing operation on a recording medium, airflow will flow into the gap formed between the slider and recording medium that rotates in a high speed. The airflow comes in from one end opposing to the other end on which the read/write portion is formed, and comes out of the slider from the other end on which the read/write portion is formed. The slider floats slightly over the recording medium due to the airflow. Thus, when airflow-caused floating happens, distance between the recording medium and ABS is named as flying height.
Decreasing of the flying height has benefit to density improvement of the recording medium, since decreasing of the flying height causes bit length of the recording medium decreasing. Therefore, it is required to control the flying height more critically according to demand of higher density of disk drive in recent years.
However, to produce airflow with proper volume between the slider and the recording medium, a concave-convex portion is formed on ABS of the slider for adjusting airflow. The convex portion of the concave-convex portion includes a read/write portion and a rail portion extending along a direction from which the airflow comes in. However, if the read/write portion is coupled to the concave portion with an angle of approximately 90 degree formed there between, that is, if the read/write portion is coupled with an edge portion of substantially right angle, turbulent airflow will be generated at position adjacent the wall of the edge portion, causing instable airflow and easy peeling off of the edge portion, both of which are undesirable. Hence, an incline portion is utilized to connect the read/write portion and concave portion. By formation of the incline portion, along the incline portion, airflow may easily enter into tiny space formed between the read/write portion and recording medium. The incline portion may also be an inclined structure formed by a curved surface segment (see patent reference 1 and FIG. 3(d) of patent reference 2).
For forming this kind of incline portion, ion milling method is used. The method is used for lapping surface of an object to be processed such as substrate in slider manufacturing process and in the method, ions are separated from plasma generated in an ion source chamber in manner of ion beam and guided out of the plasma by a guiding electrode. By forming an angle larger than 90 degree between direction along which the ion beam moves and normal direction of surface of the object being processed (i.e., the ion beam has an inclined incidence angle), and by rotating the object being processed around the normal direction, the ion beam becomes back portion of the overcoat, thus the incline portion being formed with ease. The incline portion may also be formed by reactive ion etching (RIE) method (see patent reference 3). In RIE process, lapping is performed in an environment filled with reactive gases such as CF4, CH2 and H2 to accelerate etching speed.
Patent reference 1: Japanese Application Publication NO. 2001-229514
Patent reference 2: Japanese Application Publication NO. 2002-312916
Patent reference 1: Japanese Application Publication NO. 2003-323707
As described above, it is important to control flying height of the slider for achieving higher recording density of hard disk drive (HDD). For this purpose, it is very critical to control the airflow more easily, and the incline portion needs to be manufactured to have a shape of not limited to planar or curved surface, maybe have a more suitable shape.
On the other hand, it is also important to control variations of the flying height for purpose of controlling the flying height of the slider. For this purpose, length control of the incline portion that generates big floating force thereabout is also critical, and highly precise incline portion should be fabricated without variation. In conventional technology, based on these viewpoints, ion milling method is also used to easily adjust angle of the incline portion and form an incline portion with a curved surface. However, application of ion milling method results in incline portion length variation of 4-5 times as much as that of the target value, as well as increased flying height variation. In addition, when applied to ceramic of high hardness, etching rate will be very slow, thereby causing problems such as low production efficiency.
In addition, different from ion milling in which etching direction is determined by ion incidence angle, RIE belongs to chemical etching using reactive gases, therefore, etching direction control is impossible, adjustment of incline angle and formation of incline structure with specific shape is also difficult to realize. That is, in RIE process, several seconds of time are needed from application of high frequency power to stabilization of the plasma. In this period, depth of at least 10 nm is etched, and etching action in this unstable period becomes reason of variation, thus making it difficult to form the incline structure with fine precision.